Powder compaction is a well-established process for manufacturing a wide range of
products, including engineering components and pharmaceutical tablets. During powder
compaction, the compacts (green bodies or tablets) produced need to sustain their integrity during
the process and possess certain strength. Any defects are hence not tolerable during the production.
Therefore, understanding failure mechanisms during powder compaction is of practical
significance. In this paper, the mechanisms for one typical failure, capping, during the compaction
of pharmaceutical powders were explored. Both experimental and numerical investigations were
performed. For the experimental study, an instrumented hydraulic press (a compaction simulator)
with an instrumented die has been used, which enable the material properties to be extracted for real
pharmaceutical powders. Close attentions have been paid to the occurrence of capping during the
compaction. An X-ray Computed Microtomography system has also used to examine the internal
failure patterns of the tablets produced. Finite element (FE) methods have also been used to analyse
the powder compaction. The experimental and numerical studies have shown that the shear bands
developed at the early stage of unloading appear to be responsible for the occurrence of capping. It
has also been found that the capping patterns depend on the compact shape.